package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @author lubiao
 * @date 2021/4/2
 * @desc
 */
public class SimpleExecute implements Executor{

    enum ExecuteType{
        EXECUTETYPE_QUERY,
        EXECUTETYPE_UPDATE;
    }

    /*@Override
    public <E> List<E> query(Configuration configuration,
                             MappedStatement mappedStatement,
                             Object... params) throws Exception {
        //1、注册驱动，获取数据库连接
        Connection connection = configuration.getDataSource().getConnection();


        //2、获取sql语句 select * from user where id = #{id} and username = #{username}
        //转换sql语句 select * from user where id = ? and username = ?
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);

        //3、获取预处理对象 preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());

        //4、设置参数
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterTypeClass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            //使用反射
            Field declaredField = paramterTypeClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);

            preparedStatement.setObject( i + 1,o);
        }

        //5、执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();

        //6、封装返回结果集
        while (resultSet.next()) {
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);
                //使用反射或者内省，根据数据表和实体的对象关系，完成对实体的封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }*/

    @Override
    public <E> List<E> query(Configuration configuration,
                             MappedStatement mappedStatement,
                             Object... params) throws Exception {

        ResultSet resultSet = (ResultSet) execute(configuration,mappedStatement,ExecuteType.EXECUTETYPE_QUERY,params);
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);

        ArrayList<Object> objects = new ArrayList<>();

        //6、封装返回结果集
        while (resultSet.next()) {
            Object o = resultTypeClass.newInstance();
            //元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i = 1; i <= metaData.getColumnCount(); i++) {
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);
                //使用反射或者内省，根据数据表和实体的对象关系，完成对实体的封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            objects.add(o);
        }
        return (List<E>) objects;
    }

    @Override
    public Integer update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        Integer execute = (Integer) execute(configuration, mappedStatement, ExecuteType.EXECUTETYPE_UPDATE, params);
        return execute;
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {

        if (paramterType != null) {
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作
     * 1、将#{}使用?代替
     * 2、解析出#{}里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记解析器来完成对占位符的解析工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{","}",parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql,parameterMappings);
        return boundSql;
    }


    private Object execute(Configuration configuration,
                           MappedStatement mappedStatement,
                           ExecuteType executeType, Object... params) throws Exception {
        //1、注册驱动，获取数据库连接
        Connection connection = configuration.getDataSource().getConnection();
        //2、获取sql语句
        String sql = mappedStatement.getSql();
        BoundSql boundSql = getBoundSql(sql);
        //3、获取预处理对象 preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        //4、设置参数
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramterTypeClass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //使用反射
            Field declaredField = paramterTypeClass.getDeclaredField(content);
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);

            preparedStatement.setObject( i + 1,o);
        }

        //5、执行sql
        Object object;
        if(ExecuteType.EXECUTETYPE_QUERY.equals(executeType)){
            object = preparedStatement.executeQuery();
        }else{
            object = preparedStatement.executeUpdate();
        }
        return object;
    }
}
